I take my very hot mare over a line of 3 small cross rails at 2 stride distance 2 days before the show and I don't ride her the day before. This grid allows me to work her over small jumps. I take them while in circles, but circles in between them. Take them 1,2 or 3 at a time. All the combinations to get her working with me and thinking.
But in the end it depends on the horse. My last horse I would jump him over a course at the barn the day before and he would be all set.
If the show is on Sunday, I usually jump on Wednesday. I will either work on gymnastic or a full course depending on the horse needs (and mine).
Then, I won't jump until the show. I would probably have a ride out, a lunge session and working on the flat the day before to get him relaxed and stretched.
It is my personal program, the mot important is to adapt your training to your horse. Some horses need to "see" some little jumps before the show, others don't need to jump at all.
Hope this helps :)